Field of the Invention
Embodiments of the present invention generally relate to a substrate holding apparatus and a method of using the same, and more particularly, to a substrate holding apparatus having a lift bar including a porous head and a method of using the same.
Description of the Related Art
A coating process may be performed to manufacture various products including semiconductor devices, displays, and solar cells. For example, a solution may be coated on a substrate using inkjet printing in order to form a polymer organic light-emitting layer included in an organic light-emitting display.
Here, the solution may be coated on the substrate in a state where the substrate is fixed on a stage. The substrate may be fixed on the stage by suction. Generally, a groove is formed in an upper part of the stage, and the substrate is vacuum-sucked onto the stage by a vacuum pump connected to the groove. Here, if a vacuum suction force generated at an interface between the substrate and the stage is not uniform, the surface of the substrate may become uneven. Accordingly, the solution may be coated to a non-uniform thickness on the substrate, thereby forming coating stains.
In particular, if a lift bar is installed inside the stage in order to separate the substrate from the stage by raising the substrate or place the substrate on the stage by lowering the substrate, more coating stains may be formed in a region on the lift bar which contacts the substrate.